A mechanic working on the engine of a cab-over-engine tractor often climbs into the into engine compartment and places any needed tools on top of the engine or other convenient surfaces in the compartment, or on top of one or more of the front wheels. If an additional tool is needed, the mechanic must climb out of the engine compartment to get the tool and then back into the compartment to continue working. Tool trays are shown in Diller, U.S. Pat. No. 4,341,304, designed to be supported by a front wheel of a tractor. These would be useful for temporarily holding a selected set of tools so that they can be located in one conveniently available place while the mechanic is working on an engine, but the Diller tool trays are not designed to provide a permanent holder for a large number of tools.